I have one Barred rock and she is the head hen, but she is very sweet and is not mean at all, she is just the boss. The hens that were at the lower end of the pecking order were my bullies and were very mean to my new pullets, pecking at them all the time. After being together for several months they pretty much all get along, I think there are always differnet personalities with every breed and that you can't label all chickens in a certain breed being mean. My RIR was agressive, but not really mean, I think she just did not want to end up at the bottom of the pecking order, I think that is normal chicken behavior. I wish you luck with your chickens, but I think I would always be scared they would kill again.